In the PC world, it is common for one motherboard assembly to be used in multiple mechanical form factors. For instance, a single motherboard could fit in both a tower and a desktop enclosure. However, the different form factors might have different thermal profiles with different optimal fan speed curves. In addition, one form factor might expose different motherboard I/O than another. Other parameters likewise might vary with form factor.
Simply programming the motherboard's non-volatile memory to account for the form factor in which the motherboard is to be used is less than desirable. First, it locks the motherboard to the form factor that is programmed in memory until and unless the memory is reprogrammed, typically not a chore that end users would welcome. Also, it means that the memory must be programmed correctly, and moreover the location of the form factor type in memory can be accidentally or maliciously erased. Moreover, a replacement motherboard must be updated manually.